RADIX JALAPiE. 445 



fibrous fracture; internally it is of a pale clingy brown or dirty white. 

 It has a famt smoky, rather coftee-like odour, and a mawkish taste, 

 followed by acridity. 



Microscopic Structure — Seen in transverse section, jalap exhibits 

 no radiate structure, but numerous small concentric rings, which in 

 many pieces are very regularly arranged. They are due to the latici- 

 ferous cells, differing from the suiTounding parenchyme only by their 

 contents and rather large size. These laticiferous cells traverse the 

 tissue in a vertical direction, constituting vertical bands, as may be 

 observed on a longitudinal section; the single cells are simply placed 

 one on the other, and do not form elongated ducts as in Lciduca or 

 Taraxacum. 



The fibro- vascular bundles of jalap are neither numerous nor large ; 

 they are accompanied by thin-walled cells, so that firm woody rays do 

 not occur. ParenchjTnatous cells are abundant, and, on a longitudinal 

 fracture especially, if subsequently moistened, are seen to constitute con- 

 centric layers. The laticiferous cells are always found in the outer part 

 of each layer. The suberous coat with which the drug is covered is 

 made up of the usual tabular cells. 



The parenchyme of jalap is loaded with starch grains; in the pieces 

 which have been submitted to heat in order to dry them, the starch 

 appears as an amorphous mass, and the drug then exhibits a horny 

 consistence and greyish fracture, instead of being mealy. Crystals of 

 calcium oxalate are frequently met with. The laticiferous cells contain 

 the resin of jalap in a semi-fluid state, even in the dry ding; drops of 

 the resinous emulsion flow out of the cells, if thin slices are moistened 

 by any watery liquid. 



Chemical Composition — Jalap owes its medicinal efficacy to a 

 resin, which is extractable by exhausting the drug with spirit of wine, 

 concentrating the alcoholic solution to a small bulk, and pouring it into 

 water. The resin precipitated in this manner is then washed and di'ied; 

 it is contained in jalap to the extent of 12 to 18 per cent.^ 



From this crude resin, which is the Resina jakqxe of the pharma- 

 copoeias, ether or chloroform extracts 5 to 7 (12, Umney) per cent, of a 

 resin which, according to Kayser,- partiallysolidifies when in contact with 

 water in crystalline needles. We can by no means confirm Kayser's state- 

 ment. The residue (insoluble in ether) is one of the substances to which 

 the name Jalapin has been applied.' W. Mayer, 1852-18.5.5, who desicr- 

 nated it Convolvulin,'^ found it to have the composition C^'H^O^l When 

 purified, it is colourless; it dissolves easily in ammonia as well as in the 

 fixed alkalis, and is not re-precipitated by acids, ha\'ing been converted by 

 as-sumption of water into amorphous Convolvulic Acid, which is readily 

 soluble in water. Both convolvulin and convolvulic acid are resolved by 

 moderate heating with dilute acids, or with emulsin, into crystallizable 



^ Guibourt obtained of it 17 per cent., per cent, of resin. Bronghton is of opinion 



Umney 21-5, Squibb 11 to 16, T. and H. that exposure of the sliced tuber to the air in 



Smith "not more than 15," D. Hanbury 1 1 the process of drying, favoui-s the formation 



to 15 8. Jalap grown in Bonn afforded to of resin, by the oxidation of a hydiocarbon. 

 Marquart 12 \>ev cent. ; a root cultivated at - Gmelui, Chemistry, xvi. (1864) 159. 



Munich gave Widnmaim 22 per cent. ; from ' As by Pereira, Elem. of Mat. Med. ii. 



plants produced in Dublin W. G. Smith (1850) 1463. 

 got 9 to 12 per cent.; and fine tubers from •* Gmelin, op. cit. xvi. 154. 



Ootacamund in India yielded to one of us 18 



